The failure of purely gravitational models of X-ray cluster
formation to reproduce basic observed properties of the
local cluster population suggests the need for one or more
additional physical processes operating on the intracluster
medium (ICM). We present results from 84 moderate resolution
gas dynamic simulations designed to systematically
investigate the effects of preheating - an initially
elevated ICM adiabat - on the resultant, local X-ray
size-temperature, luminosity-temperature and ICM
mass-temperature relations. Seven sets of twelve simulations
are performed for a \LambdaCDM cosmology, each set
characterized by a different initial entropy level Si.

The slopes of the observable relations steepen monotonically
as Si is increased. Observed slopes for all three
relations are reproduced by models with Si \in 55-150 keV
cm2, levels that compare favorably to empirical
determinations of core ICM entropy by Lloyd-Davies, Ponman
& Cannon. The redshift evolution for the case of a locally
successful model with Si = 106 keV cm2 is presented. At
temperatures T \geq 3 keV, little or no evolution in
physical isophotal sizes or bolometric luminosities is
expected to z \leq 1. The ICM mass at fixed T is lower
at higher z as expected in the canonical evolution model.
ICM mass fractions show a mild T dependence. Clusters with
T \geq 3 keV contain ICM mass fractions depressed by
modest amounts (\leq 25%) below the cosmic mean baryon
fraction \Omegab/\Omegam; hot clusters subject to
preheating remain good tracers of the cosmic mix of
clustered mass components. This work was supported by NASA
and NSF.

The author(s) of this abstract have provided an email address
for comments about the abstract:
jbialek@umich.edu